A conventional seat belt system comprises a length of seat belt webbing connected at three points to load-bearing parts of a vehicle. A lap portion of the seat belt webbing passes laterally across the hips of the seat occupant, and a torso portion of the seat belt webbing passes diagonally across the torso of the seated occupant from one hip to the opposite shoulder.
Typically one end of the seat belt webbing is attached to an anchor that is bolted to a load-bearing part of the vehicle on one side of the seat, usually to the seat or between the seat and an adjacent door. The shoulder end of the seat belt webbing is attached to a seat belt retractor mounted to a load-bearing part of the vehicle, for example a side pillar or sill, or directly to a load-bearing seat, optionally via a webbing guide.
The seat belt retractor increases comfort for the seat occupant restrained by the seat belt since it allows the seat belt webbing to pay out under relatively low loads to enable limited movement of the restrained seat occupant, for example to reach entertainment controls or storage compartments. The seat belt retractor is biased to keep the seat belt webbing relatively taut about the seat occupant. A locking element locks the seat belt retractor against webbing payout in the event an acceleration sensor senses a crash.
The seat belt webbing is fastened to the buckle mechanism by a buckle tongue that is slidably attached to the seat belt webbing so that the lengths of seat belt webbing making up the lap and torso portions can easily be varied to suit the size and shape of the vehicle occupant.
Known seat belt systems of this sort tend to be unsuitable for vehicle occupants of shorter than average stature, particularly for children, because the shoulder belt fastening point is located to accommodate an average person and is located at or above the height of the back of the seat. This is particularly so in rear seat safety restraints. Thus the torso portion of the seat belt tends to be badly positioned for a child or short person and usually passes too close or adjacent to the child's neck. Because the child does not fit into the adult seat belt properly, the child's shoulder can roll out of the seat belt during a crash effectively making the seat belt a two-point lap belt only. In this scenario, the lap portion alone will then take more force in a crash and will be more likely to inflict injuries than when a torso belt portion is combined with the lap portion. In addition, the child may slide under the lap portion; this is known as submarining. It is well known that children feel uncomfortable with adult seat belt restraints and often position the torso portion behind their back to reduce discomfort.
A solution to this problem is exemplified in a product known as “The Generation Belt” which provides an additional strap that is fastened taut in a generally vertical line along the front surface of the back of a vehicle seat. A shoulder support for the seat belt is slidably attached to the vertically extending strap so that its vertical position can be varied. However, the shoulder support is not retained in the desired position by anything other than friction and under high crash loads it may slide upwardly putting the shoulder support in an unsuitable position. “The Generation Belt” does not comply with the latest safety regulations of which at least one is ECE 44/03.
An alternative is to use a booster seat or cushion for a child user of an adult seat belt. However the lower mass of a typical child means insufficient force is generated during a crash for the seat belt to elongate as it would for an adult user. While the child's torso is firmly restrained, the head will swing forward to a greater extent than for an adult and will not satisfy the head injury criteria of standard safety regulations. Furthermore, the use of auxiliary child seats on public transportation, such as busses, is not always available.
In U.S. Pat. No. 7,703,806 B2 a vehicle seat belt system had seat belt webbing attached to a tongue adapted to be located in a buckle mechanism fixed to a load-bearing part of the vehicle. A generally vertically extending strap was adapted to be located in a position against a seat back. An adjustable webbing guide is connected to the generally vertically extending strap to the seat belt webbing; and there was a device for positively locking the webbing guide to the generally vertically extending strap at any one of a plurality of selectable locations on the generally vertically extending strap. A load limiter was operative for a child seat occupant but not operative for an adult seat occupant. The vertically extending strap was offered in distinguishable colors separated by a marker line to show the upper non-extensible portion of the strap and the lower extensible portion. This prior art device while an improvement was not automatic and required user intervention to insure it was properly fitted for the appropriate sized child. This introduced the concern that human error could occur and the wrong selection of selectable locations would be made. Secondarily, the vertical strap was positioned to be fully exposed in front of the exterior front surface of the seat back making it an obstruction against which adults would find objectionable.
It is therefore an object of the present invention to provide a fully automatic seat belt design with an automatic ability to adjust for different sized occupants without any manual adjustment or manipulation of the seat belt other than a normal fastening of the tongue to the buckle.
The present invention described below further achieves these objectives while concealing a large portion of a strap in or behind the seat back so the user cannot be impacted or confused by the exposure of extra straps as was the case in the prior art system of U.S. Pat. No. 7,703,806 B2.
These and other innovative features are disclosed by the seat belt system as described hereinafter.